In the last 20 years, the bee-keeping sector registered very consistent losses worldwide, in terms of bee numbers and productivity. These facts had also a negative impact on a broader scale in the agro-alimentary sector. Several factors concurred to this disaster that, only in 2007, led to a loss of 30-50% of the whole Italian and European apiarian patrimony, and of peaks of 60-70% in some areas of the USA. The damage is not limited to the insects' death or the loss of biodiversity. The whole agro-alimentary sector suffers of this problem due to insufficient pollination that can negatively impact the seasonal harvest. Economically, this corresponds to a loss of about a 1 billion /year distributed as follows: 20 million in USA, 70 million in China, 500 million in Europe, 400 million in the rest of the world. In Italy, only in 2007, 200 thousand beehives were destroyed leading to an economic loss related to missed-pollination of about 250 million euro (equivalent to 1240 euro/beehive) (from press release of APAT—Agency for the environmental protection and technical services—29 Jan. 2008). Among the possible reasons that induce this high mortality are the hygienic conditions of the beehives, the climate change, the availability and quality of feeding and water, electromagnetic pollution and contamination with phyto-pharmaceutical products (neonicotinoids). These stress factors can contribute to decrease the immune defences of the bees thus making them weaker against microbial and viral infections.
The control of microbial and viral diseases is a serious problem because nowadays there are no specific approved medicaments for this purpose. The only solution is the prevention, e.g. preventing the viral or bacterial load from reaching such a level as to induce infections. This can be attained by the adoption of the so-called Good Apiary Practice, avoiding the exchange of materials, sterilizing the instruments and maintaining good ventilation in the beehives. However, this Good Practice may not be enough and the number of epidemic events is constantly increasing. Among them the American Foulbrood Disease (AFD)—the most dangerous disease for the bees' larvae (Apis mellifera)—is of great concern because there is not yet a solution [Genersch E., 2009. American Foulbrood in honeybees and its causative agent, Paenibacillus larvae. J Invertebr Pathol. 103 Suppl 1:S10-9]. The etiological agent of the AFD is a spore-forming bacterium, Paenibacillus larvae [Genersch et al., 2006. Reclassification of Paenibacillus larvae subsp. pulvifaciens and Paenibacillus larvae subsp larvae as Paenibacillus larvae without subspecies differentiation. Int J Syst Evol Microbiol 56:501-511]. Four subgroups—each one with specific phenotypic characteristics—belong to the species P. larvae: ERIC I; ERIC II; ERIC III; ERIC IV [Raugh et al., 2009. Negative correlation between individual-insect level virulence and colony-level virulence of Paenibacillus larvae, the etiological agent of American foulbrood of honeybees. Appl Environ Microbiol 75:3344-3347]. ERIC I and ERIC II are the most diffused. This microorganism preferentially infects the young larvae. It is transmitted with the feeding by the adults that nevertheless remain healthy. The use of antibiotics to control the AFD diffusion in Europe is forbidden due to the possible development of antibiotic-resistant pathogens and for reasons of food safety [Miyagi T., Peng C. Y. S., Chuang R. Y., Mussen E. C., Spivak M. S., Doi R. H., 2000. Verification of oxytetracycline-resistant American foulbrood pathogen Paenibacillus larvae in the United States. Journal of Invertebrate Pathology 75:95-96]. At the same time, the notification to the authorities of the presence of the AFD in any of the beehives is compulsory, according to the Italian law. Moreover, in accordance with the rules of the Veterinary Police (D.P.R. 8/2/54, n. 320, art. 154-158)—due to the absence of any specific treatment—the only accepted solution is the destruction of the contaminated beehives. The aim of this drastic approach is to avoid the presence of any possible recurrent infection focuses.
As already stated above, in the greatest number of cases, the use of the Good Apiary Practice is not sufficient to avoid the presence of infection focuses.